Sound-projecting apparatus



April 10, 1928.

E. GRISSKNGER SOUND PROJEGTING APPARATUS Original Filed Julyl2, 1921 4sheets sheet 1 m 6 N Ed 2 A TTORNEY April 1928.

E. GRISSINGER SOUND PROJECTING APPARATUS Original Filed July 12, 1921 4Sheets-She t 2 IN VENTOR f/Imad G g- ATTORNEY April 10, 1928. 1,666,057

E. GRISSINGER SOUND PROJECTING APPARATUS Original Filed July 12, 1921 4h et 5 i 29 l L 55 g 4 a 5A A jy l I? y [I H IHHHH MANIA /58 INVENTORf/n ooo Gain/27591 A TTORNE Y E. GRISSINGER April 10, 1928.

S OUND PROJECTING APPARATUS IN V EN TOR f/n oaa @vbslhfer 1 A TTORNE Y 4Sheets-Sheet 4 Original Filed July 1921 lit Lil)

Patented A r. 10, 1928.

UNITED STATES PATENT OFFICE.

ELWOOD GRISSINGER, OF BUFFALO, NEW YORK.

SOUND-PROJECTING APYARATUS.

Original application rfiled July 12, 1921, Serial Ihl'o. 484,240.Divided and this application filed August 18, 1923. Serial No. 658,007.

My present invention relates to cabinets of the'type employed foramplifying and projecting sound waves, particularly phonograph cabinets.Its novel features are closely related to and preferably include certainnovel features of the projector which is set forth and separatelyclaimed in my companion application Serial No. 484,240, filed July 12,1921, and which issued as Patent No. 1,477,556 on December 18th, 1923,of which application this is a division. The novel features of theamplifier and projector which make possible the 'novel cabinet structureherein claimed, are indicated in the drawings and will be describedherein to such extent as may be necessary to an understanding of the newand useful features of the cabinet in which it is embodied.

In my cabinet the air column comprises the tone arm, an intermediateportion in which the expansion is mainly or wholly lateral, and aterminal portion in which the expansion is mainly in the otherdimension. Of these, the intermediate portion is of extreme practicalimportance because in cabinet phonographs as now manufactured it isimpractical to continue the small diameter conduit around all of thecurves which are required because of the limitations of the cabinetmakers art and the necessity of providing a considerable physical lengthof air column in which the wave front must be gradually expanded to therequired large area before projecting it into the open air. This is oneof the advantages of my invention. I am able to start the expansiondirectly at the outlet of the tone arm, but in one dimension only, sothat the conduit may be curved to almost any desired extent in the thindirection without danger of serious phase displacement for the shortlength waves. lt'is to be noted, however, that curvature either of asmall diameter pipe or of a thin layer conduit is not a good a} thingacoustically. Hence, in the preferred form of my invention, the middleportion of the air column is made fairly straight (downward for thecabinet type of phonograph}, the waves are turned iate-raily outwardthrough the side of the cabinet, being permissible to turn them throughvery wide angles in the direction of thinness of the beam,

by thus intimately associating the slender part of the air column whichis in the tone arm, with an equal or greater length and breadth ofwidened air column, the otherwise sharply resonant air column in thetone arm tends to function with the widened air column as a compositeunit of which said widened air column is a more or less dominant part.

1 The widened portion may be curved in the direction of its thinnessthrough an arc of 90 degrees or more, provided the radius of curvaturebe not too sharp, without substantial impairment of its function.Consequently it is quite possible to arrange the projector outlet in thefront face of the cabinet and have the intermediate conduit curved asmuch as may be necessary to bring, its small end in receiving relationto the passage through which the tone arm discharges downward.

-At the endof the widening conduit, the wide thin sound beam ispermitted guided but high angle expansion in a vertical direction. Up tothe vertically expanding projecting portion, it seems desirable to keepthe main beam as thin as may be practical, without choking the exit ofsaid beam, although this seems to be an energy problem and thedesideratum seems to be to have the beam fill the throat without chokingit.

Another feature of my invention consists in arranging the tone armoutlet at the front of the phonograph cabinet directly over theprojector outlet. This makes desirable another feature of my invention.which consists in arranging the sound box so that the stylus needletrails toward the vertical axis of the tone arm, on the right hand sideof the center of a record, which, as usual, rotates clockwise. Thismakes it convenient for right-hand manipulation of the sound box torenew the needle or re tate the same into and out of operating relationto the record. A further feature is mounting the sound box upon ballbearings, for rotation about an axis which coincides with the axis ofthe sound outlet of said box.

The above and other features of in vention may be more fully understoodfrom the following description in connection with the accompanyingdrawings, in which 2- K Figure l is a vertical section along centralaxis of the sound amplifier and pro jester showing diagrammatically thepath of the main beam and also a part of the forward diffusion thereofnear the mouth the line 4-4, Fig. 3.

Fig.- 5 is a plan View of a modification.

These drawings are intended to indicate approximate sizes as well as theproportions of the parts in one desirable embodiment of my invention.The scale for Figs. 1 and 2 is indicated on Figs. 2, but Figs. 3, 4 and5 are on a scale twice as large.

In these drawings the invention is shown as applied to a cabinet type ofphonograph having a top 1, bottom 1' sides 1", 1 and front 1 The top 1carries the motor box 2 driving turn table 3 supporting record 4 inoperative relation to sound box 5 having diaphragm 6 operated by astylus lever 7 through needle 8. These parts may be of any known ordesired construction, but as above indicated, thesound box preferablyembodies the invention set. forth in my application Serial No. 404,860.

The top 1 also carries the tone arm 9 on standard 14; also the primaryexpansion conduit 10 and the reflecting, secondary-expansion projector11, which opens through the side 12 of the cabinet.

The diaphragm 6 has its inner face in operative contact through opening13, with the upper end of the air column which extends continuouslythrough said parts 9, 14:, 10, 15 and 11 to the outer air. j

The diameter of the air column may be say inch to inch for the length ofthe tone arm 9, but in the device shown this is.

enlarged to about 1% inches in the standard 14. Then for the next 14inches or through the expansion chamber, the air column has afront-to-rear contraction to say 1 inches, while the lateral widening inthe same distance is approximately 14 inches. The next 4 inches measuredalong the axis of the main beam, follows the reflection path, and iscontained in a portion of the projector which actually measures onlyabout 1% inches from front to rear. The path of'the beam from the end ofsaid reflection path out to the mouth of the projector is about 8 inchesto 10 inches though the shortest distance to the mouth is say 4 inchesto 6 inches. This is short as compared with lengths of either tone armor primary expension conduit. The final expansion in the verticaldirection is also limited as to angle, being preferably between top andbottom means? walls diverging at angles less than 90, preferably about60 to The horizontal width of the mouth across the face of the cabinetis preferably the same or slightly greater than that of the slot outletat 15. Usually it will be found convenient and acoustically desirable tomake this horizontal width about the same as the practically permissiblewidth of the cabinet.

The entire widening ,cbn-duit 10, together with the entire reflectingprojector 11 might well be embodied in one integral gray iron castinghaving walls say inch or more in thickness, but as actually constructedby me and as shown in the drawings, the intermediate widened section 10is made of 16 gauge hard rolled sheet brass the sides being cut topattern and soldered at the corners. The transverse sectionis'substantially rectangular throughout. At'the upper end the sheetbrass is firmly screwed and brazed to a square bushing 16 which is inturn screwed to the top 1. At the lower end the slotlike outlet isreinforced by a stiff brass frame member 17 which is in turn screwed tothe top board 18 of the reflecting projector. As will be evident fromFig. 2, particularly, the front and rear walls of the widening section10 are of very considerable area and the sheet brass employed beingrelatively thin, would be liable to vibration in response to the soundwaves. Consequently, I have reinforced and stifi'ened these fiatareas'by longitudinal channel bars 19, 20, 21 brazed in place andclamped by superposed cross bars 22, 23, held by tension bolts 2323".The channel bars determine nodal lines and the unclamped areas betweenthe tire conduit in a plaster of Paris or concrete jacket.

When this part of the device is an integral metallic casting, theinterior surface may be contmuous and smooth throughout and, if desired,the exterior maybe ribbed instead of clamped.

The reflecting projector 1l constituting the secondary expansion elementis made of hard elastiematerial smoothly finished on the inner surfaces,preferably well seasoned birch about 9;; inch to 1 inch or more inthickness. widened in a horizontal direction to the maximum extentbefore reachin the projector, the end walls 10%, 10 o the pro- The beambeing preferably the following features of construction which are ofacoustic as well as structural advantage. The tone arm has its verticalaxis at the front of the cabinet, that is, aboveand near the outlet ofthe projector which opens through the side of the cabinet. The wavesfrom the tone arm can be carried almost directly downward and whatevercurvature is necessary, as for instance that shown in I Fig. 1, is inthe direction in which the air column is thin. Atthe same time the aircolumn is being expanded in the other dimension, at a high rate.Frictional losses and particularly attenuation of the high frequenciesis very small because/the expansion is so free and the distance soshort. By the time the waves reach the reflecting projector,

the wave front has been expanded so that the distance and therefore thevelocity-of oscillation of the air particles in propagating the wave, isgreatly decreased. As friction decreases much more than in directproportion to decrease of velocities, the frictional losses are muchreduced. Moreover, the propagation of the waves in this part of the aircolumn being by reflection from hard polished surfaces, losses for thehigher frequencies are small.

In my projector the waves, without having to traverse any curves afterthey have been expanded more than two inches in the direction of thecurve and without having to turn any corners except by high anglereflection, are enabled to traverse an air column which, as we have seenabove, is 36' inches or more in length, yet the main beam emerges fromthe mouth of the projector not more than 8 inches or 10,inches from thebase of the tone arm outlet.

The thus compactly disposed air column affords the desired quarter wavelength column for the generation of the long waves of the lowestfrequencies necessary for phonosame side of the cabinet through whichthe graph work, and at the same time, affords a low friction,phase-preserving path for the high frequencies upon which the quality ofthe reproduced sound depends.

The novel location of the tone arm on the .sound is projected into theouter air, would require a tone arm and sound box of usual construction,to trail on the left-hand side i of the record which would be awkwardand inconvenient in practice. Accordingly my invention includesarranging the sound box to operate on the right hand side of the recordwith'the stylus trailing toward the vertical axis of the tone arm. Thepreferred construction for this purpose is illustrated in Figs. 1 and 2.The tone arm 9 is curved around through a right angle to form ahorizontal terminal portion 29. On this is mounted a housing 30 in whichmay be fitted an ordinary, ready-assembled roller bearlng con'iprisingouter ring member 31, the intermediate balls 32 and the inner ringmember" 33. The latterhas fitted within the same a relatively longsleeve 33', on the outer end of which the sound box is secured by meansof screw 34. A face plate 35 closes in and protects the ball race.Outside of the housing 30 is secured a spring 36 adapted to frictionallyengage and retain the sound box 1 when turned to the uppermost positionfor removal or insertion of the needle or for discontinuing operation ofthe phonograph. The weight of the'projection 37 and housing 38 on thesound box may be adjusted to cause the stylus to bear upon the recordwith any desired degree of force. While this mounting for the sound boxis of special advantage in connection with. my present invention, it isobvious that any known or desired sound box. and any known or desiredmounting thereof may be employed.

While I have described in great detail the characteristics of oneillustrative form of a composite air column, and the. structure wherebyall of the various features are practically attainable, it will beobvious that the perfect reproduction obtainable by this invention iscontributed by and is the composite result of numerous very novelfeatures localized at various points along the air column, each of whichrepresents careful study, invention and discovery by itself, as well'asin relation to the whole. For instance, it is in the nature of adiscovery that where the air column is expanded in one dimension only,the expansion may be very rapid, provided the other dimension besulficiently thin; that preferably this other. di-

mension is less than 2 inches that when the K thinning in of thisdimension gets down toward a half inch and. less, the length and widthof conduit required to give the desired enlargement .of wave front maybecome great, that is, say 24 inches or even 36 inches for a inch slot,and that the limitations on slot thicknesses are of particularimportance with reference to the higher frequencies to be reproduced.Another instance is discovery of the desirability for the thinness ofmain sound beam in connection with a reflecting projector, and thedesirability of narrowing the throat. so that. the sound may fill thesame. Another instance is the discovery, involving more or less of theforegoing, that the best way to expand a wave is to give it primaryguided expansion in one dimension, keeping the other dimension small,preferably well below 2 inches until expansion in said dimension isadequate, then affording the wave a guided and limited, but neverthelessrapid secondary expansion in planes at right angles to the primaryexpansion.

\Vhen I speak of expansion in one dimension followed by expansion inanother dimension the word dimension is not to be taken in a strictlygeometrical sense, that is to say, it is the spacing and proximity ofthe front and rear walls of conduit 10, that is of importance so far asconcerns the broader aspects of the invention involved. It the spacingand proximity be preserved these walls could be given a curvature in adirection parallel with the waves. As an extreme illustration, thedesired proximity of the walls could be preserved where one wall is acone and the other wall an inner cone concentric with the first. In thisparticular case the benefit or a downwardly curving wave front crossingthe mouth of the projector at difierent distances and times and angles,will he lost unless the mouth of the conduit were cut on a plane at anangle to the axis of the cones. This instance is cited merely as anillustration oi "the fact that some oi my dis coveries are generic andapplicable to geometrical torms of air column quite difierent from thoseshown in the drawings.

While the vertical end walls of the projector month are above describedas parallel, the principal value of this is cheapness of constructionThey may diverge or converge provided the angle be not too abrupt. Withrespect to lateral difiusion of the sound, in the outer air, it will benoted that the 24.. inch slot does not sound as loud as the let inchslot when front of the respective in= struments, whereas, from anadjoining (side) room, the i l linch slot will not sound as loud as the24 inch slot, at least this is so for many kinds of records.

With respect to the length for conduit ill,

' it will be noted that if a conduit 14 inches by 14 inches by 1 inchmakes the edge portions of a given wavefront or given wave phase 2inches or ll inches behind the axial portion, when assing the mouth 15,then a conduit 28 inc es by 28 inches would make this distance 4 inchesto 6 inches so that the 28 inch conduit would give the same phasedifferences for a wave front of frequencies an octave lower than wouldthe 14 inch conduit.

For waves of average phonographic intensity the area to which theconduit 10 widens the wave front, is preferably between 12 square inchesand 30 square inches, although inferior but fair results have beenobconduit, the outlet area of which is only 7 square inches. A 24 inchby 24 inch by 1 inch having an area of 2a inches gave almost as goodresults as a 16 inch by 16 inch by 1 inch which had an area of 20inches. The latter is perhaps the most satisfactory instrument of allthe instruments I have specifically described.

The mouth portion of the projector wherein the thin beam is thickened tothe desired final area is preferably-shorter than the axial length ofthe primary conduit and shorter than the width of the beam projectedtherefrom.

F ig. 5 shows a tone arm which is bent horizontally in reverse curves,so as to bring the vertical plane of the trailing stylus needle into thesame plane with the vertical pivotal axis of the tone arm. Thefrictional drag of the record on the needle is made to take effect inthe plane of the vertical axis and there is less tendency for the needleto jump the groove in the record or to press more strongly on one sideof the groove than on the other. ln the term shown these reverse curvesresult in increasing the length of the tone arm several inches, as willbe evident by comparison with the form shown in Fig. l.

While l have shown and described with considerable precision the precisedimension! as well as the shape of one desirable embodiment of Ill?invention to other with illustrative examples of how certain oi thesedimensions can be varied to advantage, it will be evident that certainof the claims herein define the combinations in such scope as to includedifferent dimensions, proportions and details of construction, such asshown in my patents such as 1,477,553 and 1,5535%; and such claims areintended cover said combinations whether employed in the sensitivesonorous plate combinations to which said prior disclosures are morespecifically direct ed, or in the non-vibratory wall combinations towhich my present application is more specifically directed.

It will be noted that some of the novel features of organization andarran ent of the parts of the phonograph cabinet as claimed hereinresemble those disclosed in m prior application Ser. No. 380,492 filedMl 11, 1920, now Patent 1553370 but I have elected to present thecabinet structure claims in this application and to limit the claims ofsaid prior application to specific features not specifically claimedherein.

While the theories herein stated are such as may prove helpful in thedesign of other devices embodying various features of m invention,separately or in difi'erent combination or relation, the completenessand accuracy of some of them have not been fully verified and applicantreserves the right to lid tain'ed with a. 14 inch by 14 inch by inchwithdraw, correct or supplement some of said theories, in accordancewith the facts which may be developed by further study or test.

I claim:

1. A phonograph cabinet having the usual record-supporting and drivingmeans and any known or desired reproducer and tone arm defining aslender air column in operative relation thereto, the vertical axis ofthe tone arm being located approximately in the central front-to-rearvertical plane of the cabinet and discharging downward, said cabinetbeing of substantially greater diameter than said record supporting anddriving means in combination with a primary expansion conduitcommunicating directly with the slender part of the air column, saidconduit expanding the waves to a relatively wide, thin beam anddelivering said beam through a projector dischargin through a side Wallof the cabinet and h tically divergin walls adapted to afford limitedand guide but rapid expansion of the wave front in the dimension inwhich the beam is thin, the mouth of said projector having a widthapproximating the width of said-cabinet.

, 2. In the combination specified by claim 1 the further feature of acurve in the conduit to bring its outlet in desired relation to theprojector said curve being in the direction.

of the thinness of said conduit.

3. In the combination s ecified by claim 1 the further feature of deecting surfaces in the projector whereby the sound beam is deflectedthrough a total are approximating a semi-circle.

4. In the combination specified by claim 1 the further feature of havingthe throat or outlet of the widening conduit of a height approximatelyequal to or less than the thickness of the sound beam where it isprojected from the mouth of the conduit.

. 5. A phonograph'apparatus comprising a cabinet, a re roducer,supporting and rotatingmeans or the record and a tone arm swmging in ahorizontal plane, upon the free end of which said reproducer is'mounted, but with the reproducer needle trailing toward the front 'ofthe cabinet and the tone arm discharging downward at the front of thecabinet, in combination with a conduit in which the waves from the tonearm are expanded laterally, in a length at least as great as the lengthof the said slender part of the air column and to a width several timesits thickness.

6. A phonograph apparatus comprising a cabinet, 9. reproducer,supporting and rotating means for the record, arrd a tone arm defining aslender air column in operative rela tion to the reproducer; the tonearm discharging downward at the front of the cabinet; 8. sound outlet inthe front of the cabiaving vernet and intermediate means for expandingthe waves to a limited extent; then pro ecting them through said outletin the front of the cabinet, said outlet having a width approximatelythat of said cabinet. I

7. A phonograph apparatus comprising a cabinet, a reproducer, supportingand rotating means for the record, and a tone arm defining a slender aircolumn in operatlve relation to the reproducer; the tone arm dischargingdownward at the front of the cabinet; in combination with a downwardlyextending conduit shaped to expand the waves widely in a dimensionparallel with the front of the cabinet substantially without expansionin the other dimensions, and means for projecting the thus expandedwaves outwardly through the front face of the cabinet 7, the furtherfeature of plane reflectors in the projector whereby the sound beam isemitted at an upward angle.

9. In the combination specified by claim 7 the further feature ofarranging the plane reflectors at right angles and closely adjacent, inthe same wall of the projector to direct the emitted sound beam adjacentthe roof or upper wall of the projector outlet. 10. A cabinet typephonograph including a cabinet having therein the projector outlet andthe tone arm outlet adjacent the same face of the cabinet .andincombination with the reproducer and tone arm of such a device, amounting for the reproducer 'onthe tone arm permitting rotary motion ofthereproducer about an axis substantially perpendicular to the center ofthe reproducer diaphragm, the reproducer stylus trailing toward thevertical axis of the tone arm so as to operate on the right hand side ofthe center of the record.

11. In the combination specified by claim 10 the further feature of aroller bearing concentric with the axis of the reproducer diaphragm andin which bearing the reproducer turns, in combination with means foryieldingly forcing the stylus toward the record by rotary movement aboutsaid axis.

12. A phonograph apparatus comprising a cabinet, a reproducer,supporting and rotating means for the record, and a tone arm defining aslender air column in o erative relation to the reproducer; in comination with a projector opening through a wall of the cabinet and anintermediate conduit in which the waves from the slender part of the aircolumnare expanded laterally, to form a thin beam approximately as wideas the projector opening, said projector having walls, ra id y diver ingvertically to the desired eight of t e outlet opening.

\ in one dimension to a wide thin beam, said 13. A phonograph cabinetapparatus comprising supporting rotating means for the record, areproducer, and a tone arm defining a slender air column inoperativerelation to the reproducer; in combination with a projector having amouth opening through a vertical wall of the cabinet and an intermediateconduit communicating directly with the outlet of the tone arm, andshaped so as to expand the waves mainly projector having wallspermitting wide expansion of said beam in the direction of its thinness.

14. A phonograph cabinet apparatus comprising supporting rotating meansfor the record, a reproducer, and a tone arm defining a slender aircolumn in operative relation to the reproducer; in combination with aconduit communicating directly with the outlet of the tone arm, saidconduit having its walls shaped so as to expand the waves to a wide thincross section, the width of which is several times the thickness.

15. In combination with the parts specified 'by claim 14 two high anglereflectors arranged to reflect said beam twice in the direction of itsthinner dimensions.

16. In the combination specified by claim 14 the further feature ofhaving the wider walls of said conduit approximately parallel for aconsiderable distance back from the outlet thereof.

17. A method of sound wave amplification comprising expanding the soundwaves substantially in one dimension'only and then expanding themsubstantially in another dimension only.

18. A method of sound wave amplification comprising expanding the wavessubstantially in one dimension only, then deflecting them in thedirection of their thinness, and then expanding them in substantiallyanother dimension only.

19. A method of amplifying sound waves comprising causing substantiallyuni-dimensional expansion only of the waves successively in diiferentdimensions.

Signed at Buffalo, in the county of Erie and State of New York, thisv31st day of July, A. D. 1923.

ELWOOD GRISSINGER.

